JPS5931014B2 - distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a distance measuring device using pulsed laser light.

Pulsed laser distance measuring equipment generates a gigantic laser pulse with an extremely short time width, irradiates it towards the target object to be measured, receives the reflected laser light, projects the laser light, and then processes the process until it is received. It attempts to measure the distance to the target by measuring the time.

First, related parts of a conventional device of this type will be explained with reference to FIG.

In Figure 1, 1 is a charging power source, 2 is a capacitor that charges the output of the charging power source 1, 3 is a choke coil that limits the current when the capacitor 2 is discharged, and 4 is a laser oscillation due to the discharge energy from the capacitor 2. 5 is a laser oscillator, 5 is a receiving optical system that collects the laser reflected light from the target, 6 is a photodetector that receives the light from the receiving optical system 5 and converts it into an electrical signal, and 7 is a photodetector 6. A load resistor 8 is a power supply that applies a bias drive voltage to the photodetector 6, and 9 is a video amplifier that amplifies the output signal.

In the above device, a charging power source 1 charges a capacitor 2 with a predetermined amount of energy.

The energy E is expressed as: (1) E = -CV2 (J) (1) where C - capacitance of capacitor (unit: farad) V - charging voltage (unit: volt).

In a normal distance measuring device, a voltage of around 1000V is selected.

The laser oscillator 4 receives the discharge energy from the capacitor 2 and generates a huge pulsed light having an extremely short time width.

Note that the choke coil 3 is used to limit the peak current during discharge.

In order to measure the distance to a target with such a configuration, a laser beam is emitted toward the target, and some of the laser light is reflected back with a time delay depending on the distance.

The light is collected by a receiving optical system 5 and provided to a photodetector 6.

Incidentally, in recent devices of this kind, a YAG (yttrium, aluminum, garnet) crystal doped with Nd (neodymium) is often used as a laser oscillation element from the viewpoint of efficiency and the like.

In this case, the wavelength of the laser light is 1.06 μm, which is near-infrared invisible light.

In this case, an APD (avalanche, photodiode) made of silicon is generally used as a photodetector in view of sensitivity and the like.

A reverse bias voltage is applied to the APD by a power source 8, and the voltage is usually several hundred volts.

When light is applied to the photodetector 6, a light receiving current flows depending on the intensity of the light, and is detected as a signal voltage by the load resistor 7.

The video amplifier 9 is for amplifying the received pulse signal to a predetermined size.

Although not shown in Figure 1, the distance measuring device also has a counting circuit as its main function, which calculates the distance R by measuring the time t from when the laser beam is emitted to when the received signal is obtained. , -t R--(2) where it is given by the velocity of the C binary.

Incidentally, this type of device is often used as a portable device, and it is desirable that the device be as small and lightweight as possible.

To achieve this, it is necessary to use as few parts as possible and to maximize the efficiency of the power supply, etc.

The present invention was made from this point of view, and eliminates the need for a power source conventionally used to drive a photodetector, and instead uses the electric charge charged in a capacitor necessary for laser oscillation.

The present invention will be explained below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, in which a charging power source 1, a capacitor 2, a choke coil 3, a laser oscillator 4, a receiving optical system 5, a photodetector 6, a load resistor 7, a video amplifier 9 is the same as the conventional one.

10 is a voltage judge, 11 is a relay, and 12 is a bias capacitor.

Voltage determiner 10 closes the contact of relay 11 when the voltage of capacitor 2 is rising during charging, and charges bias capacitor 2 in the same way.

When the bias voltage to the photodetector 6 reaches the optimum value, the relay 11 is opened and the capacitor 2 is connected to the capacitor 2.
Cut the eggplant.

The operation is shown in Fig. 3.

Normally, when a distance measurement command is received, a laser distance measurement device uses a capacitor 2.
is charged, and when it reaches a predetermined value, the laser oscillator 4 is driven.

The operating voltage of the photodetector 6 is selected to be lower than the charging voltage, and remains approximately constant until receiving light enters.

When an APD or the like is used as the photodetector 6, its bias current is extremely small.

Furthermore, since a distance measuring device usually measures a single target, it basically only needs to be capable of photoelectric conversion of pulsed light.

Therefore, as a power source, a capacitor charged every time distance measurement is sufficient.

Further, the voltage determiner 10 can be easily realized using a comparator such as an ordinary IC.

As explained above, according to the present invention, there is no need for a conventional power source that generates a voltage of several hundred volts from a battery as a primary power source, especially in a portable device, and it is possible to significantly reduce the weight of the device, and even when the device is on standby, the battery cannot be used as it is. A device with improved power consumption can be provided.

It goes without saying that the present invention can be realized by using a thyristor instead of the relay 11 used in the embodiment and by controlling the gate for controlling conduction of the thyristor with the voltage determiner 10.

Furthermore, it can also be realized by connecting a resistor that limits the charging current and a backflow prevention diode in series and using the same at the relay 11 position.

In this case, the resistance value is selected so that a predetermined voltage is accumulated in the bias capacitor 12 before the laser beam is oscillated.

Therefore, it can be realized without using the voltage determiner 10.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional distance measuring device, FIG. 2 is a block diagram showing an embodiment of the distance measuring device of the present invention, and FIG. 3 is a diagram explaining the operation of the distance measuring device of the present invention. be. In the figure, 1 is a charging power supply, 2 is a capacitor, 3 is a choke coil, 4 is a laser oscillator, 5 is a receiving optical system, 6 is a photodetector, 7 is a load resistor, 8 is a power supply, 9 is a video amplifier, and 10 is a A voltage judge, 11 is a relay, and 12 is a bias capacitor. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1. A power source that generates high voltage, a capacitor that stores the power output energy, a laser oscillator that generates a cipher laser beam by discharging the energy stored in the capacitor, and an electric signal that receives the reflected light from the target of the laser beam. What is claimed is: 1. A distance measuring device for measuring the distance to a target cloth, characterized in that a driving voltage for the photodetector is obtained from the energy stored in the capacitor.